Metal forming machine



Dec. 20, 1949 R. CREIGHTON METAL FORMING MACHINE 5 Sheets-Sheet 3 "LEE-l Filed May 24, 1945 NVENTOR S gan CREaeH'I-ON NEY Patented Dec. 20, 1949 UNITED STATES PATENT OFFICE METAL FORMING MACHINE Russell Creighton, Kenmore, N. Y., assignorto General Riveters, Inc., Buffalo, N. Y.

Application May 24, 1945,.Serial No. 595,595

6 Claims. 1

This invention relates to metal forming machines and particularly to machines wherein sheets of metal or similar material are permanently deformed by the application of pressure and heat.

In fabricating sheet metal it is frequently desired to use countersunk rivets, and for this reason it is common to form beveled depressions in metal sheets around and concentric with preformed rivet holes to accommodate countersunk heads. This operation is commonly known in the art as dimpling and is conventionally done as a cold die operation. In the case of certain alloys, however, for instance high tensile strength aluminum alloys, conventional cold dimpling cannot be accomplished because of unusual behavior and characteristics of the particular alloys.

I have found that a proper degree of local heat ing of the work piece makes it possible to form permanent and wholly satisfactory countersink formations or dimples, in these hitherto troublesome metals and the present application discloses apparatus and a mode of operation for attaining the desired results in a commercially workable manner.

The accompanying drawings show one specific form of apparatus by way of example and a complete description thereof is set forth in the following specification, which likewise sets forth full details as to time and temperature ranges suitable for dealing with high tensile strength aluminum alloys; however, it is to be understood that the apparatus may be variously modified and the temperatures and times employed will vary with the particular alloy being dealt with. The principles of the present invention are not limited to the specific example included herein but are to be measured only as defined in the appended claims. For one thing, reference is had above to preformed rivet holes, but if any other considerations should so dictate, the dimpling may precede the forming of the rivet hole without affecting the principles set forth herein.

The high tensile strength aluminum alloys mentioned in the foregoing are well known to those skilled in air frame fabricating and analogous arts. For instance, the Aluminum Company of America designates its high tensile aluminum alloy 758, that of Reynolds Metals is designated No. 301, and that of Ryan Aeronautical Corporation is called T81. The same apparatus and principles may be employed in dealing with other alloys of similar behavior characteristics with respect to present considerations, for instance, magnesium alloy sheets.

In the drawing. I

Fig. 1 is a side elevational' view of one formof apparatus for practicing the present invention with portions of the casing broken away for added clearness;

Fig. 2 is a fragmentary top plan view of the apparatus of Fig. 1 with the casing or framework in cross section;

Fig. 3 is a fragmentary view taken similarly to Fig. 1 but showing only the upper portion of the.

apparatus with the casing or framework likewise in cross section; and

Fig. 4 is a cross sectional view taken in a vertical plane on an enlarged scale through the punch and die mechanism per se.

Throughout the several figures of the drawings, like characters of reference denote like parts and the numeral l0 designates" generally a press framework or casing including a hollow upright pedestal portion H having a laterally projecting hollow base [2 and a head portion l3 likewise projecting laterally therefrom to form a work receiving gap between the; base and the head portion. In the form shown, the base I2 has rigidly secured thereto a ll-shaped element l3 which serves as a horn and supportsa lower die means I4, which will presently be described in further detail. I.

An upper die is designated generally I5 in Fig. 1 and is secured to an upper ram l6 which .has bearing in the headed portion l3 of the frame for vertical reciprocation. An air cylinder I1 is provided with an operating piston l8 which is fixed to the upper ram H5 in any convenient manner.

The upper and lower dies are shown in detail in vertical cross section in Fig. 4 and reference will now be had thereto. The lower die, which has been designated generally l4, comprises a central male die element 22, whose lower end 23 is provided with a stud 24, which is screw threaded into horn l3. A pin 25 normally prevents movement of the stud 24 with respect to the portion 23 of the male die element. The upper end of die element 22 has a reduced portion 21 and a bevel portion 28, which forms the male die surface for countersinking a work piece. For convenience in placing the perforation of a work sheet over the reduced portion 21 of die element 22, its upper end is rounded as shown. A collar 30 provides a spring pad for supporting the work piece above the die surface at the beginning of an operation and for stripping the work from the die after a formation has been made. For resiliently supporting the collar 30 in its illustrated position, a coil spring 32 seats at 3 its lower end in a cup-shaped member 33 which has screw threaded connection with male die element and rests upon a plate 34 which in turn rests upon a hexagonal wrench enlargement 35 formed on die element 22. The enlargement 35 seats against the upper face of horn I3.

An inverted cup-shaped member 30, which may be formed integrally with collar 30, is disposed over the upper end of spring 32 and has an outwardly directed flange 39 at its lower end. Screws pass freely downwardly through flange 39 and thread into collar 34 and the proportions of the screws, the cup-shaped member 38 and the spring 32 are such as to provide a predetermined desired initial tension in spring 32 when the parts are in their rest positions, as illustrated in Fig. 4.

The upper female die element is designated 43 and has a hexagonal formation 42 and a reduced upward extension 44, which is retained in a chuck element 45 by means of a set screw 46. The chuck element 45 has a reduced upper portion 47 provided with a stud 48 which is screw threaded into a holder 49, and the stud 48 is pinned to chuck element 45 as at 50. The holder 49 has a flange at its upper end, and the flange 5| co-operates with an inwardly flanged collar 52, which is held to the lower end of ram I6 by means of screws 53. The flange 5| and the flange of collar 52 retain the upper die against ram I6, but, as illustrated in Fig. 4, sufficient lateral clearance is provided to permit shifting of the axis of the female die by loosening the screws 53. The female die may thus be accurately registered with the lower male die. The bottom face of female die element 43 has a beveled recess 55 which comprises the female die surface and an extension recess 56 for receiving the reduced portion 21 of male die element 22 which thus serves further as a guide or leader pin.

Both the female die element 43 and the collar 30 associated with male die element 22 have annular recesses designated 56 and 51, respectively, and collars designated 58 and 59 respectively are pressed over the female die element 43 and collar 30 and thus co-operate to form annular heating passages about the die elements. The collar 58 has a lateral spout portion 60 for receivin a flame or other heat stream from a jet 6|. The collar 59 has a similar spout formation 63 for receiving flame from a jet 64. The spout 63 is larger vertically than spout 60 because it moves vertically during operation in a manner which will presently appear, while the jet 64 is relatively fixed with respect to horn I3 during normal op eration. The collars 58 and 59 have openings as at 65 and 66, respectively, which serve as discharge passages and permit a continuous flow of hot gases in passages 56 and 51. The openings 65 and 66 may be multiplied about collars 58 and 59 as desired to insure suiiicient capacity and distribution of the discharge flow.

The manner in which reciprocation of the piston I8 in cylinder I1 is effected, and with it the ram I6 and upper die means l5, will now be described. In this connection reference will be had particularly to Figs. 2 and 3 wherein the numeral I0 designates a conduit leading from a source of fluid pressure, for example compressed air. The conduit I9 may include a standard air filter and a standard lubricator, these elements being designated II and I2 respectively in Figs. 2 and 3. The conduit I0 extends to one port of a four-way solenoid operated valve 13 which is a commercially available unit and accordingly need not be described in detail.

As indicated fragmentarily in Fig. 2, conduit I0 is in permanent communication with a port I4 of valve I3. In the idle position of the machine, port "I4 is connected with port I5 which has a fixed conduit connection I6 with the lower portion of cylinder I I, whereby the piston I8 is held in its elevated position. In Fig. 2, the exhaust port of the four-way valve I3 is designated I8 and, likewise in the idle position of the machine, port I0 is connected with port I9 which is permanently connected with the upper side of cylinder II by means of conduits BI, 82, and 83, in order, the conduit 82 including a check valve 86 which permits free fiuid flow from cylinder II to port I9 but closes against retrograde flow. In the idle position of the machine the upper end of cylinder II is thus vented to the atmosphere through exhaust port I8.

In addition to the conduit portion 82, conduits 8| and 83 are connected by two additional alternative conduits 90 and 9|. The conduit 90 includes an automatic pressure regulatin valve 94 which is available as a standard unit and which, in the present apparatus, is adjusted to permit fluid passage from conduit 8| through conduit 90 to conduit 83 only up to a predetermined pressure, for instance 10 lbs. per square inch. The conduit 9| includes a normally closed solenoid-opened valve 95 having an operating solenoid 96. The valve 95 and the solenoid 96 are available as a unitary commercial unit.

In Fig. 3, conductors I00 and IOI lead from a power source by way of a foot operated treadle switch designated I03 in Fig. 1 and branch conductors I05 and I06 extend to the operating solenoid of four-way valve I3. Other branch conductors I08 and I09 connect the conduits I60 and "II with solenoid 96 of valve 95, but these conductors extend by way of a time delay device I I I, which is a standard commercial unit, one form of which is known in the art as a Square D timer.

When the circuit of conductors I 00 and NI is closed by operation of the treadle switch I03 energization of the operating solenoid of four-way valve I3 is immediate, but energization of the solenoid 96 which opens valve 95 is delayed for a predetermined period depending upon the adjustment of the timer III. In the present apparatus this adjustment may be for a period of the general Order of from two to fifteen seconds.

The operation of the pressure means for recip-- rocating piston I8 and accordingly effecting operating cycles of the die means will now be described. When treadle switch I03 is closed by the operator of the machine, the solenoid of valve I3 is immediately energized and the port connections of valve I3 are shifted so that pressure inlet port I4 connects with port I9 leading to the upper side of cylinder I! and port I5, leading from the lower side of cylinder II, is simultaneously connected with exhaust port I8. The check valve 86 blocks conduit 82 and conduit 9| is still closed by valve 95 but pressure is introduced to the upper end of cylinder II by way of conduits 8|, 90 and 83, the degree of pressure being automatically limited by regulating valve 94. Under the limited degree of pressure thus afforded, female die I5 lowers to engage the work piece and somewhat compress spring 32 and thus lower collar 30; however, the pressure made available is not enough to compress spring 32 to a degree which will begin the actual dimpling formation.

In this position of the parts collar 30 and female die 43 are engaged resiliently but firmly against opposite faces of the work sheet and transmit their heat thereto by conduction through an annular zone beginning inwardly at the circle defining the ultimate dimpling formation and extending outwardly therefrom. The setting of the timer III is such that valve 95 opens automatically after the work sheet has been heated to the required degree. When valve 95 opens automatically the full pressure of the compressed air source from conduit I0 is conducted to the upper side of cylinder H, the collar 30 is-further depressed against the resistance of spring 32, and the desired dimple is die-formed between the male and female die surfaces 28 and 55. When the switch H33 is opened by removal of the operators foot, four-way valve 73 returns automatically to its initial position and the piston is raised by pressure through conduit I6, free egress of fluid from the upper end of cylinder I? being permitted by reason of return conduit portion 82 leading to the exhaust port 18 and the check valve 8% which opens freely to fluid flow in this direction.

In the form of invention shown in Fig. 1, the heating medium comprises an oxy-acetylene arrangement and an oxygen tank I20 and an acetylene tank I ZI may be housed in the pedestal I I of the machine. Conventional gauges and regulating valves are illustrated and an oxygen conduit I22 and an acetylene conduit I23 lead to a standard mixer I24 which has two outlet conduits, I25 and I26, each of which receives a proper mixture of oxygen and acetylene from mixer I24. The conduit I25 leads to jet BI and a conduit I26 to jet 64, as appears from Fig. 1.

The horn I3 is pivotally mounted on base I2, 3

by means indicated generally at I2? in Fig. 1, for free movement about a vertical axis coincident with the vertical axis of the die means, whereby the horn I3 may be swung about to accommodate under hanging portions of a work piece being operated upon without disturbing the working relationship of the upper and lower die means. It is accordingly desirable to run the conduit I26 up through the axis of pivotal movement of horn I3, as shown in Fig. 1, whereby pivotal movement of horn I3 will not interfere with proper and continuous passage of fuel to jet 64.

Jet 54 extends from a block I30 which is pivotally connected to a pair of arms I3! which are in turn pivoted to horn I3. In this way arms I3! may be adjusted about their pivot on horn I3 to bring the jet 64 closer to or farther from the die means and block I38 may be pivoted upon arms I3I an amount sufficient'to retain the correct direction of emission of the flame from jet 64. Upper jet 6! is fixed to a block I which is pivoted to arms I36 which have adjustable pin and slot connection with head I3 of frame I 0. By this means jet SI may be adjusted upwardly or downwardly and also toward and away from the female die means and its ultimate direction of emission may also be adjusted by adjustment of block I35 with respect to arms I36.

When dealing with the high tensile aluminum alloys hereinbefore specified die temperatures between 400 and 600 degrees Fahrenheit produce good results, the optimum being probably about 550 degrees F. When dimpling for a one-eighth inch countersunk rivet in sheets between about .015 inch and .032 inch thick the holding period of female die 43 and collar 30, prior to final for ing by male die element 22, is of the order of several seconds. Obviously, thicker sheets will require longer holding periods than thinner sheets to provide adequate conductive heating of the part of the metal which is subject to adequate forming.

What is claimed is:

1. Sheet metal forming apparatus comprising a male die and a coaxial female die element, means supporting said male die and said female die element for relative axial reciprocation toward and away from each other, a sleeve element surrounding the male die and resilient means urging the sleeve element toward the female die element whereby the sleeve element and the female die element engage a work sheet in advance of forming engagement between the male die and the female die element during their relative reciprocation toward each other, means for heating one of said elements for heating work sheets engaged therebetween about the portions to be formed by conduction from said element, means actuable to move said male die and said female die element relatively toward each other with a force less than the force required for metal forming engagement therebetween against the resistance of the resilient means to move said heated element to heat conducting position, and time delay means actuable to subsequently move said male die and said female die element to metal forming position.

2. Sheet metal forming apparatus comprising a male die and a coaxial female die element, means supporting said male die and said female die element for relative axial reciprocation toward and away from each other, a sleeve element surrounding the male die and resilient means urging the sleeve element toward the female die element whereby the sleeve element and the female die element engage a work Sheet in advance of forming engagement between the male die and the female die element during their relative reciprocation toward each other, means for heating one of said elements for heating work sheets engaged therebetween about the portions to be formed by conduction from said element, means actuable to move said female die element and said sleeve element relatively toward each other into heat conducting engagement with a Work sheet, and time delay means actuable to subsequently relatively move said male die and said female die element to metal forming position.

3. Sheet metal forming apparatus comprising coaxial male and female die elements, means supporting said elements for relative axial reciprocation toward and away from each other, a sleeve surrounding the male die element and resilient means urging the sleeve toward the female die element whereby the sleeve and the female die. element engage a work sheet in advance of forming engagement between the male and female die elements during relative reciprocation of the die elements toward each other, means for heating said female die element and said sleeve for heating work sheets engaged therebetween about the portions to be formed by conduction from said female die element and said sleeve, means actuable to move said die elements toward each other to such heat conducting position with a force less than the force required for metal forming engagement between said die elements against the resistance of said resilient means, and time delay means actuable to subsequently move said die elements to metal forming position.

4. Sheet metal forming apparatus comprising coaxial male and female die elements, means supporting said elements for relative axial reciprocation toward and away from each other, a sleeve surrounding the male die element and resilient means urging the sleeve toward the female die element whereby the sleeve and the: female die element engage a Work sheet in advance of forming engagement between the male and female die elements during relative reciprocation of the die elements toward each other, means for heating said female die element and said sleeve for heating work sheets about the portions to be formed by conduction from said female die element and said sleeve, means for moving said die elements partially toward each other to move the female die element and said sleeve into heat conducting engagement with a work sheet, and time delay means actuable to subsequently move said die elements to metal forming position.

5. Sheet metal forming apparatus comprising male and female die elements, means supporting said elements for relative reciprocation toward and away from each other, resilient means surrounding the male die element and cooperating with the female die element to engage resiliently against the work sheet ahead of the male die element during relative reciprocation of the die elements toward each other, means for heating said female die element and said means surrounding the male die element for heating work sheets engaged therebetween adjacent to the portions to be formed by conduction from said female die element and said male die surrounding means, means actuable to move said die elements toward each other to heat conducting position with a force less than the force required for metal forming engagement between said die elements against the resistance of said resilient means, and time delay means actuable to subsequently move said die elements to metal forming position.

6. Sheet metal forming apparatus comprising male and female die elements, means supporting said elements for relative reciprocation toward and away from each other, resilient means surrounding the male die element and cooperating with the female die element to engage resiliently against the work sheet ahead of the male die element during relative reciprocation of the die elements toward each other, means for heating said female die element and said means surrounding the male die element for heating work sheets adjacent to the portions to be formed by conduction, means for moving said die elements partially toward each other to move female die element and said resilient means into heat conducting engagement with a work sheet, and time delay means actuable to subsequently move said die elements to metal forming position.

RUSSELL CREIGHTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,014,815 Rutledge Sept. 17, 1935 2.255 116 Helmstaedter Sept. 9, 1941 2,288,378 Veit June 30, 1942 2372,516 Rechton et al. Mar. 27, 1945 2,396,218 Watters Mar. 5, 1946 OTHER REFERENCES Pp. 24-29 of Journal of Aeronautical Sciences, vol. 18, No. 1, November 1940. 

